A portable telephone set such as a mobile phone or a personal handyphone system (abbreviated as “PHS”) has been reduced in size and weight enough to be put in a pocket owing to the progresses of the semiconductor technology, the electronic circuit technology, the casing machining technology and the like. Therefore, it has remarkably become so widespread that the number of subscribers exceeds that of stationary telephones. A person, who always possesses a portable telephone set, also can utilize various functions in addition to its original telephone functions since a CPU is used for a control operation. Specifically, the portable telephone set has a function of electronic telephone book or address book, a calendar function, a clock function, a recording function (a sound memo function), a mail function, a browser function and the like. Thereafter, it can provide even a user having little opportunity of utilizing a telephone with various utilizing methods, thereby enhancing the availability. As the number of functions increases, the functional difference between the portable telephone set and a personal digital assistant (abbreviated as “PDA”) has become smaller. Thus, the portable telephone set can also function as a portable, small-sized and simple personal computer.
Input keys for the above-described portable telephone set generally consist of numeral/character input keys, scroll keys for the purpose of item selection, arrow keys and four-direction keys. However, since the use frequency of the portable telephone set has become higher as the functions of an electronic mail, a browser and the like have been enhanced in recent years, there has been a demand for the configuration of an easy key input operation in addition to a small size.
A portable telephone set capable of satisfying the above-described demand is disclosed in, for example, Japanese Patent Application Laid-Open No. 270072/2000, in which there are only two key buttons, i.e., an up-down and right-left button (a cross button) and a selection button, there are numeral rows (1, 2, 3 . . . ) and character rows (a, ka, sa, ta, na . . . or A, B, C . . . ) on a display, and then, characters and numerals can be input by selecting one of the numerals and characters displayed and designating conversion/non-conversion, a small letter/a capital letter, hirakana/katakana or the like. Consequently, operability can be secured while achieving miniaturization.
Otherwise. Japanese Patent Application Laid-open No. 32113/1999 discloses that a track ball and three keys, i.e., a communication key, a termination key and a cancel key, are disposed in place of conventional ten keys, wherein selection of a numeral or an item, retrieval of an abbreviated dial number and the like can be performed by operating the track ball like a cross key.
However, in the case of the conventional portable telephone set disclosed in Japanese Patent Application Laid-Open No. 270072/2000, a cursor for selecting an item to be displayed on a display screen can be moved only in horizontal and vertical directions, but cannot be moved in slantwise directions Therefore, if the cursor is intended to be moved from coordinates (x, y) to other coordinates (x+3, y+2), the up-down and right-left button need to be moved three times in the lateral direction and twice in the vertical direction. That is to say, five key operations need be performed in total. In this way, although an improvement in operability is directed, in fact, the operation of a frequent finger motion is required, and thus, this key input system is inconvenient for a user.
Also in the case of the conventional portable telephone set disclosed in Japanese Patent Application Laid-Open No. 32113/1999, since there is no numeral key, it is difficult to input a telephone number or the like, and further, since the setting position of the track ball is restricted to a conventional numeral key position, operation like a mouse cannot be performed while a main body is kept to be gripped. What is worse, the display or item selection with respect to information obtained via the track ball is restricted only in the vertical and lateral directions, and the track ball cannot be moved (or selected) in slantwise directions.
In recent years, a notebook-sized personal computer or a handheld personal computer has remarkably become widespread, and the Internet can be readily utilized as soon as a user buys it or if he or she only adds a simple adapter. Therefore, if the user brings the notebook-sized personal computer or the handheld personal computer (hereinafter referred to as “a portable type personal computer”) together with a portable telephone set on a private trip or on a business trip, he or she can perform communications without any connection to a public telephone network via a cable.
The portable type personal computer gives first priority to the portability, and therefore, a small size and a light weight are achieved to the limit. Consequently, a mouse incorporated in a personal computer body (or disposed near a keyboard unit) is poor in operability in comparison with a mouse of an external connection type via a cable. So, many users bring the mouse of an external connection type having good operability. However, unless the personal computer is used, the mouse of an external connection type becomes an obstacle, thereby inducing inconvenience in portability.